Simplify the following expression: $z = \dfrac{1}{8y} + \dfrac{3}{2y}$
In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $8y$ and $2y$ $\lcm(8y, 2y) = 8y$ $ z = \dfrac{1}{1} \cdot \dfrac{1}{8y} + \dfrac{4}{4} \cdot \dfrac{3}{2y} $ $z = \dfrac{1}{8y} + \dfrac{12}{8y}$ $z = \dfrac{1 +12}{8y}$ $z = \dfrac{13}{8y}$